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Updated: May 15, 2026
A High-throughput, High-content, Liquid-based C. elegans Pathosystem
Published on: July 1, 2018
Identification of Pseudomonas aeruginosa phenazines that kill Caenorhabditis elegans
Brent Cezairliyan1, Nawaporn Vinayavekhin, Daniel Grenfell-Lee
1Department of Genetics, Harvard Medical School, Boston, MA, USA.
Abstract:
Pathogenic microbes employ a variety of methods to overcome host defenses, including the production and dispersal of molecules that are toxic to their hosts. Pseudomonas aeruginosa, a Gram-negative bacterium, is a pathogen of a diverse variety of hosts including mammals and the nematode Caenorhabditis elegans. In this study, we identify three small molecules in the phenazine class that are produced by P. aeruginosa strain PA14 that are toxic to C. elegans. We demonstrate that 1-hydroxyphenazine, phenazine-1-carboxylic acid, and pyocyanin are capable of killing nematodes in a matter of hours. 1-hydroxyphenazine is toxic over a wide pH range, whereas the toxicities of phenazine-1-carboxylic acid and pyocyanin are pH-dependent at non-overlapping pH ranges. We found that acidification of the growth medium by PA14 activates the toxicity of phenazine-1-carboxylic acid, which is the primary toxic agent towards C. elegans in our assay. Pyocyanin is not toxic under acidic conditions and 1-hydroxyphenazine is produced at concentrations too low to kill C. elegans. These results suggest a role for phenazine-1-carboxylic acid in mammalian pathogenesis because PA14 mutants deficient in phenazine production have been shown to be defective in pathogenesis in mice. More generally, these data demonstrate how diversity within a class of metabolites could affect bacterial toxicity in different environmental niches.
Insights
Pseudomonas aeruginosa produces toxic phenazines that kill the nematode Caenorhabditis elegans. Phenazine-1-carboxylic acid is the primary toxin, activated by acidic conditions, suggesting a role in host defense.
Area of Science:
- Microbiology
- Toxicology
- Biochemistry
Background:
- Pathogenic microbes produce toxins to overcome host defenses.
- Pseudomonas aeruginosa (P. aeruginosa) is a Gram-negative bacterium that infects various hosts, including mammals and the nematode C. elegans.
- Phenazines are a class of molecules produced by P. aeruginosa with known toxic properties.
Purpose of the Study:
- To identify phenazine molecules produced by P. aeruginosa strain PA14 that are toxic to C. elegans.
- To characterize the toxicity of identified phenazines, including their pH-dependence.
- To elucidate the role of specific phenazines in P. aeruginosa pathogenesis.
Main Methods:
- Bacterial culture and toxin production assays.
- Nematode toxicity assays using C. elegans.
- High-performance liquid chromatography (HPLC) and mass spectrometry for phenazine identification and quantification.
- pH-dependent toxicity studies.
Main Results:
- Three phenazines, 1-hydroxyphenazine, phenazine-1-carboxylic acid, and pyocyanin, were identified as toxic to C. elegans.
- Phenazine-1-carboxylic acid is the primary toxic agent, with toxicity activated under acidic conditions produced by P. aeruginosa.
- Pyocyanin toxicity is pH-dependent but not under acidic conditions, and 1-hydroxyphenazine is produced at sub-lethal concentrations.
Conclusions:
- Phenazine-1-carboxylic acid plays a significant role in P. aeruginosa pathogenesis towards C. elegans, particularly in acidic environments.
- The differential toxicity and environmental activation of phenazines suggest distinct roles in various host niches.
- Understanding phenazine-mediated toxicity provides insights into bacterial pathogenesis and host-pathogen interactions.
